1. Field of the Invention
The present invention relates to a proximity sensor comprising: a detection coil assembly including a coil and a core; a circuit assembly incorporating an oscillation circuit having a coil as a resonant circuit element and an output circuit for generating an output signal based on an oscillation state of the oscillation circuit; a plug-adaptable connector; and a cylindrical outer shell case for accommodating all of these components integrally connected with each other.
2. Description of the Related Art
Aproximity sensor employing a flexible spring tongue piece for the electrical connection between a circuit assembly and a connector has been known as one kind of proximity sensor comprising: a detection coil assembly including a coil and a core; a circuit assembly incorporating an oscillation circuit using the coil as a resonant circuit element and an output circuit for generating an output signal based on the oscillating condition of the oscillation circuit; and a connector, all of which are integrally connected with each other and accommodated in a cylindrical outer shell case.
To be more specific, in this proximity sensor, the printed circuit board (corresponding to the circuit assembly) is provided on both sides with terminal parts for the electrical connection with the connector, and is also provided on the connector side with a spring tongue piece which leads to the conductive terminal projecting from the plug outlet and which comes into contact with the terminal parts on the circuit board by sandwiching the printed circuit board.
This proximity sensor can establish electrical connection between the printed circuit board and the connector only by inserting the connector from the rear-end side of the outer shell case into which the printed circuit board has been fitted (see Japanese Unexamined Patent Publication No. 5-144524 (1993)).
The present applicant has suggested in a prior application (Japanese Unexamined Patent Application No. 2001-75117) a proximity sensor employing a flexible connection member as an electrical connection member for its components; a detection coil assembly including a coil and a core; and a circuit assembly incorporating an oscillation circuit using the coil as a resonant circuit element and an output circuit for generating an output signal based on the oscillating condition of the oscillation circuit, which are integrally connected with each other and accommodated in a cylindrical outer shell case.
In this proximity sensor, the circuit assembly comprises a detection circuit-equipped board (detection circuit assembly) containing a detection circuit that includes an oscillation circuit which uses the coil of the detection coil assembly as a resonant circuit element and that generates an object detection signal according to the oscillating condition of the oscillation circuit, and an output circuit-equipped board (output circuit assembly) containing an output circuit which drives an output element based on the object detection signal. This detection circuit assembly and the output circuit assembly are coupled with each other by a flexible connection member so as to make the distance from the detection coil assembly to the output circuit assembly variable, thereby enabling the same sensor main components (a detection coil assembly, a detection circuit assembly, an output circuit assembly, and other components integrally coupled) to be fixed into various outer shell cases of different lengths.